Zahradníková A, Minarovic I, Venema R C, Mészáros L G
Department of Physiology & Endocrinology, Medical College of Georgia, Augusta 30912, USA.
Cell Calcium. 1997 Dec;22(6):447-54. doi: 10.1016/s0143-4160(97)90072-5.
We have recently reported [Mészáros L.G., Minarovic I., Zahradníková A. Inhibition of the skeletal muscle ryanodine receptor calcium release channel by nitric oxide. FEBS Lett 1996; 380: 49-52] that nitric oxide (NO) reduces the activity of the skeletal muscle ryanodine receptor Ca2+ release channel (RyRC), a principal component of the excitation-contraction coupling machinery in striated muscles. Since (i) as shown here, we have obtained evidence which indicates that the NO synthase (eNOS) of cardiac muscle origin co-purified with RyRC-containing sarcoplasmic reticulum (SR) fractions; and (ii) the effects of NO donors on the release channel, as well as on cardiac function, appear somewhat contradictory, we have made an attempt to investigate the response of the cardiac RyRC to NO that is generated in situ from L-arginine in the NOS reaction. We found that L-arginine-derived NO inactivates Ca2+ release from cardiac SR and reduces the steady-state activity (i.e. open probability) of single RyRCs fused into a planar lipid bilayer. This reduction was prevented by NOS inhibitors and the NO quencher hemoglobin and was reversed by 2-mercaptoethanol. We thus conclude that: (i) in isolated SR preparations, it is possible to assess the effects of NO that is generated from L-arginine in the NOS reaction; and (ii) cardiac RyRc responds to NO in a manner which is identical to that we have previously found with the skeletal channel. These findings suggest that the direct modulation of the RyRC by NO is a signaling mechanism which likely participates in earlier demonstrated NO-induced myocardial contractility changes.
我们最近报道了[梅萨罗斯L.G.，米纳罗维奇I.，扎赫拉德尼科娃A.一氧化氮对骨骼肌兰尼碱受体钙释放通道的抑制作用。《欧洲生物化学学会联合会快报》1996年；380：49 - 52]，一氧化氮（NO）可降低骨骼肌兰尼碱受体Ca2 +释放通道（RyRC）的活性，该通道是横纹肌兴奋 - 收缩偶联机制的主要组成部分。由于（i）如本文所示，我们已获得证据表明心肌来源的一氧化氮合酶（eNOS）与含有RyRC的肌浆网（SR）组分共同纯化；以及（ii）NO供体对释放通道以及心脏功能的影响似乎有些矛盾，我们试图研究心脏RyRC对在NOS反应中由L - 精氨酸原位生成的NO的反应。我们发现L - 精氨酸衍生的NO使心脏SR中的Ca2 +释放失活，并降低融合到平面脂质双分子层中的单个RyRC的稳态活性（即开放概率）。这种降低被NOS抑制剂和NO淬灭剂血红蛋白阻止，并被2 - 巯基乙醇逆转。因此我们得出结论：（i）在分离的SR制剂中，可以评估在NOS反应中由L - 精氨酸生成的NO的影响；以及（ii）心脏RyRc对NO的反应方式与我们之前在骨骼肌通道中发现的相同。这些发现表明，NO对RyRC的直接调节是一种信号传导机制，可能参与了先前证明的NO诱导的心肌收缩性变化。
